参考答案

正确答案：D
解析：Listen again to part of the conversation. Then answer the question.
"Together, all three parts of the water-top, middle, and bottom-make up the blend of light that we see. Under certain circumstances, one may dominate the others. For example, in shallow water, light from the bottom is most important. In deep water, very little light comes from below, so reflections from the surface are the brightest." "So, that means, in a shallow puddle, the bottom is well lit, so it sort of contributes more to the scene. I mean, it affects the overall color more than ... say uh ... the invisible bottom of the ocean?"
Why does the student say this:
"So, that means, in a shallow puddle, the bottom is well lit, so it sort of contributes more to the scene. I mean, it affects the overall color more than ... say uh ... the invisible bottom of the ocean?"
The student's purpose is to check her understanding of what the tutor said. She says So, that means Then she repeats the tutor's explanation in her own words to check whether she understands correctly. (2.3)